Preheat oven at 180xb0C. Line a 9X7" baking sheet (to make a sheet cake) or a 6" round tin with baking paper or grease well and keep aside.
Into a large bowl, sieve the dry ingredients. Keep aside.
In another bowl, whisk the egg, yogurt, oil, powdered jaggery and sugar for 3-4 minutes till well combined and frothy.
To this, slowly add the dry ingredients and combine with a whisk or fork. Add 3-4 tbsp of milk as it will be quite thick at this stage and whisk into the batter. Into this mix in gently the chopped strawberries and frozen blueberries.
Scrape out the batter into the lined baking tin.
Bake for 20 mins in case of 9X7 tin or for 30 mins in case of 6" round tin, in both cases, testing with a skewer if it comes out clean.
Cool for 10 minutes after which you can cut as desired and serve hot with a dusting of icing sugar using a small sieve.